Electric Fans May Do More Harm Than Good In A Heat Wave

Researchers say that when temperatures rise above 95 degrees, a fan might make you even hotter, and maybe even sick.

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Originally published on July 14, 2012 12:26 pm

Assuming you can't spend a heat wave bobbing up and down in some cool body of water, the next best option is to hunker down inside with air blowing on you, right?

Preferably it's from an air conditioner set on arctic chill.

But if there's no AC, then an electric fan would be the next best thing, wouldn't you think?

Well, it turns out health experts aren't so sure about electric fans. And they say using one in a really brutal heat wave can sometimes do more harm than good.

In an editorial accompanying a review of studies from around the world on the effectiveness of electric fans, researchers writing this week in the The Cochrane Library say there's no evidence that fans are the way to go during a heat wave.

In fact, they say, that when temperatures rise above 95 degrees, or roughly body temperature, the fan might actually make you even hotter, unable to sweat and sick. There's some disagreement as to how, but some researchers have found hot air blowing on a hot body can cause an increase in the rate of dehydration or heat exhaustion.

Kay Dickersin, director of the Center for Clinical Trials and the U.S. Cochrane Center, based at Johns Hopkins University, says how the body copes with heat is very complex.

"Public health departments have a responsibility to help people prepare for a heat wave, and there are certain things they can recommend that may be evidence-based," says Dickersin. "But there are other things like use of electric fans that we really don't know much about."

Given the uncertainty, Mike Clarke, an expert on methodology research at Queen's University Belfast and one of the authors, says researchers need to tackle this with a large randomized trial.

Dickersin agrees that it would be great to do a trial, but says it would be very difficult to set up in advance of a heat wave and then once it had started. "Unfortunately it takes a tragedy to stimulate us to test an intervention properly," she says.

Increasingly, public health experts are admitting that there's a lot that they don't know about the ideal ways to keep cool in a heat wave. But they're eager to figure it out, given how risky heat waves can be, especially for the elderly, young and infirm. Heat is now the most deadly weather-related risk in the U.S., according to the Centers for Disease Control and Prevention. It's more dangerous than freezing cold or tornadoes.

Just consider the death tolls of some of the recent scorchers. There were 30,000 deaths in Europe in 2003, and more recently, the at least 46 deaths in the U.S. in late June and early July.

Heat waves are of course unpredictable — we'll never know when the next one is coming. But climates scientists say we're in store for more of them, more often. And the first six months of 2012 is already on the books as the warmest half-year on record, according to the National Oceanic and Atmospheric Administration.

Editor's Addendum:

After we posted this story, we received an email from comedian Drennon Davis, who informed us that he performs a bit specifically dedicated to NPR and fans. Check out this video of him on Vimeo.